Neighborhood context is associated with the mental health of neighborhood residents, including non-specific psychological distress, and adolescents may be especially vulnerable. However, since most research has been observational, rather than experimental, it is potentially biased. Neighborhood-health research typically models point-in-time exposures of neighborhoods, in lieu of understanding neighborhood exposure trajectories, and insufficient attention has been paid to the specific contexts navigated by minority, impoverished, adolescent girls. Our study proposes a secondary analysis of data from a social experiment of voluntary neighborhood relocation using Section 8 Vouchers in 5 cities (the Moving to Opportunity, MTO, Study), to test how and why random assignment of an offer to move to a low-poverty neighborhood improves female adolescent psychological distress over a 4-7 year period. We will complement the existing data with additional neighborhood-level data collection to enrich the dataset. Randomization is the gold standard for establishing causation and MTO is the only available large-scale study that has randomly assigned individuals to receive different neighborhood contexts. Yet prior MTO analyses have not fully integrated theoretical understanding of female adolescent development to motivate the empirical analyses. Nor have prior analyses probed why neighborhoods reduce the psychological distress of girls, whether certain subgroups are more likely to benefit than others from the neighborhood relocation, or whether there are important developmentally-sensitive periods when exposure to neighborhood deprivation may be especially influential on the mental health of teenage girls. Our project proposes 3 aims: Aim 1: To test, among adolescent girls, whether the association between moving to a low-poverty neighborhood and psychological distress is mediated by neighborhood characteristics, family context, or individual risky behavior;Aim 2: To examine whether the effect of moving to a low-poverty neighborhood on psychological distress among adolescent girls is modified by baseline health status, or other family or adolescent vulnerability;Aim 3: To compare the importance of alternative timing or sequencing patterns of exposure to neighborhood poverty on adolescent distress. The project will leverage an interdisciplinary team of investigators, including fields of social epidemiology, demography/sociology, develop- mental psychology, psychiatric epidemiology, and statistics. This project will capitalize on the MTO experimental design, to apply innovative methods infrequently used in epidemiology to understand causation and mediation (instrumental variable analysis), and to explore how causal methods to model time-varying neighborhood exposures (structural nested models) can inform our understanding of developmental processes for adolescent well-being. Because of the rigorous experimental design, this project can provide strong evidence on the mechanisms by which social policies like Section 8 housing vouchers may improve population health by addressing upstream determinants of mental health such as place-based deprivation. PUBLIC HEALTH RELEVANCE: The results of this project, leveraging a social experiment of housing relocation, have the potential to inform the literature on why neighborhood context is a cause of psychological distress in adolescent girls, including probing more specificity on when and for how long living in low-poverty neighborhoods may be most beneficial for adolescents. This knowledge will inform the next generation of interventions and policies to ensure that all girls may benefit from neighborhood relocation, and/or to inform community improvement interventions, and ultimately reduce distress among women.